As a disc-type, multistage airbag-use gas generator, a structure has been disclosed where the inside of a cylindrical housing having gas outlets is partitioned by a partition wall into plural combustion chambers disposed side-by-side in the axial direction of the cylindrical housing. Inside the cylindrical housing, inner cylinder members having peripheral walls in which plural flash holes are disposed and inside spaces in which igniting means are accommodated are disposed penetrating the partition wall and are welded to a bottom wall of a diffuser shell and to a closure shell (see patent document 1).